Field of Invention
The present invention relates to semiconductor devices, and more particularly to a semiconductor device and method for manufacturing the same.
Background
An electrically erasable read-only memory (EEPROM) device can retain stored data when the power supply is removed. It can erase data already stored in the memory and reprogram the memory. An EEPROM device is an important data storage device. It stores data by applying a voltage to a control gate so that electrons can tunnel through a tunnel oxide layer into a floating gate to store the data. However, with the continuous advance in semiconductor technology and application requirements, the ever-decreasing feature size of the EEPROM device imposes stricter requirements to device manufacturing processes. This is due to the smaller size of the EEPROM tunneling oxide layer relatively to the Flash memory device. For example, for an EEPROM device below 0.15 um, the width of the tunnel oxide layer is about 90 nm. The tunnel oxide layer is generally manufactured using advanced lithography and etching processes to define a small channel, and the channel is then processed in a furnace. However, due to the limited resolution of conventional lithography processes, the channel size is relatively large after exposure and development processes, so that the 90 nm channel requirement for a 0.15 um technology node cannot be met.
Current techniques for solving the limited lithography resolution focus on the development of advanced lithography technology and equipment; however, advanced lithography equipment requires a large capital investment and is expensive to operate and maintain. Thus, there is a need for a novel method for solving the above problems.